The present invention relates to an optical head for a recording apparatus used for recording and reproducing (writing and reading) information (data) at a high density by detecting an interaction between light and a very small area of a surface of a record medium by utilizing light, and more particularly, to a near-field light information recording apparatus for observing structural information or optical information at a very small area equal to or smaller than a wavelength of incident light for use in information recording and reproduction at a high density.
In recent years, the development of an apparatus for recording and reproducing information at a high density utilizing light, such as an optical disc, has been intensely pursued. For high density information: storage, it is necessary to shorten a wavelength of light by utilizing ultraviolet light or the like; however, there is a limit to such reduction. Therefore, there is a method for effectively reducing the wavelength of light using an objective solid immersion lens. Another method of effectively shortening a wavelength utilizes near-field light for constituting a component of a wave number by an imaginary number.
A high resolution probe utilizing near-field light is used in a near-field optical microscope or a near-field optical head. By generating near-field light from a front end of a probe and detecting propagated light generated as a result of an interaction between the near-field light and a sample of a microscope or a recording medium, a spatial resolution exceeding the diffraction limit of light is obtained. There is also a method of detecting near-field light generated as a result of an interaction between incident propagated light and a sample or a record medium by a probe. A near-field light microscope achieves a resolution exceeding the diffraction limit of a conventional optical microscope by use of this principle. Further, when such a near-field optical probe is utilized in a near-field optical head, there can be achieved a data recording density exceeding that of a conventional optical disk.
According to a data storage apparatus using a near-field light head, the basic constitution is the same as that of a conventional magnetic disk apparatus a near-field light probe is used in place of a magnetic head. By such structure, the near-field light probe maintains a constant posture in operation relative to a surface of record medium by a flexible structure. When a length direction of a suspension arm is defined as z-axis, a direction orthogonal to the z-axis and in parallel with the record medium and a vertical direction are defined as x-axis and y-axis respectively, a typical flexible structure is referred to as flexure structure having a slider that is connected to a frame-like structure only in the x-axis direction on an inner side of the frame-like structure connected to the suspension arm only in the z-axis direction. By such a structure, the frame-like structure is provided with a rotational degree of freedom with respect to the z-axis and the slider is provided with a degree of freedom with the x-axis as a rotating axis relative to the frame-like structure. That is, the slider is provided with rotational degrees of freedom with z-axis and x-axis as axes thereof relative to the suspension arm.
In making light incident on the slider relative to the suspension arm constituted in this way, an optical fiber or a waveguide is connected to the slider or light is irradiated to an upper face or a side face of the slider.
However, when light is made incident on the slider by the above-described structure, connection of some member, such as the waveguide, to the slider hinders free movement of the slider, it is difficult to maintain the posture of the slider and a distance between a surface of the record medium and a very small aperture cannot be maintained constant. When the distance between the surface of the record medium and the very small aperture is not constant, optical intensity related to the interaction is not made constant and a stable output signal cannot be provided. In order to carry out high-speed recording/reproduction, it is necessary to reduce noise. However, noise reduction becomes difficult when the signal is not stabilized. Further, when light is made incident on the slider by aerial propagation, it is extremely difficult to move incident light in synchronism with the movement of the slider. When light is made incident on an upper face of the slider by the aerial propagation, it is necessary to arrange structure for light reflection above the slider and this poses a problem in that the entire apparatus becomes large-sized.
In order to resolve the above-described problems, according to a first aspect of the invention, there is provided an optical head comprising a slider supported by a suspension arm providing a load weight, provided with air bearing force by a movement thereof relative to a record medium and producing a clearance between the record medium and the slider by a balance between the load weight and the air bearing force, a flexible structure by which the slider can change a posture thereof relative to the suspension arm, an arm-to-slider light guiding structure for projecting light from the suspension arm to a surface of the slider, an aperture formed at a bottom face of the slider for interacting with the record medium via light, and an in-slider light guiding structure for projecting light from the surface of the slider to the aperture, wherein information is recorded and reproduced by the interaction between the record medium and the aperture via the light when the slider scans the surface of the record medium, and wherein the flexible structure is integrated with the arm-to-slider light guiding structure.
According to the first aspect of the invention, when the slider scans the surface of the record medium, the slider and the suspension arm are connected and light is conveyed from one to the other with high and stabilized efficiency while maintaining the posture of the slider constant relative to the surface of the record medium. Thereby, a stable output signal is provided and high-speed recording/reproduction can be carried out. Further, in comparison with related art in which the flexible structure and the arm to slider light guiding structure are separated from each other, downsizing of the entire apparatus is realized.
Further, according to a second aspect of the invention, there is provided an optical head according to the first aspect, wherein the flexible structure is fabricated with an optical waveguide formed thereon.
According to the second aspect of the invention, in addition to an effect realized by the first aspect of the invention, the flexible structure is fabricated from a single substrate and accordingly, fabrication steps can be simplified and the optical head can be fabricated at a low cost.
Further, according to a third aspect of the invention, there is provided the optical head according to the first aspect, wherein the flexible structure is fabricated by adhering or forming the light guiding structure to the surface or the inner portion of the flexible structure.
According to the third aspect of the invention, in addition to the effect realized by the first aspect of the invention, the flexible structure and the light guiding structure can be fabricated by existing technology and the optical head can be fabricated at a low cost.
Further, according to a fourth aspect of the invention, there is provided the optical head according to any one of the first through the third aspect of the optical heads wherein the arm-to-slider light guiding structure is constituted by a structure having a small light propagation loss.
According to the fourth aspect of the invention, in addition to an effect realized by the first aspect through the third aspect of the optical heads, light loss in guiding light between the arm and the slider can be minimized.
Further, according to a fifth aspect of the invention, there is provided the optical head according to any one of the first through the third aspect of the optical heads wherein the arm to slider light guiding structure is formed in a linear line or a shape having a small radius of curvature.
According to the fifth aspect of the invention, in addition to the effect realized by the first aspect through the third aspect of the optical heads, light loss in guiding light between the arm and the slider can be minimized.
Further, according to a sixth aspect of the invention, there is provided the optical head according to any one of the first aspect through the fifth aspect of the optical heads wherein the aperture is as small as a size equal to or smaller than a wavelength of light and the light interacting with the record medium is near-field light.
According to the sixth aspect of the invention, in addition to the effect realized by the first aspect through the fifth aspect of the optical heads, by utilizing super resolution that is a characteristic of the near-field light, a record density exceeding the diffraction limit of light is realized. Further, with regard to each of effects realized by the first aspect through the fifth aspect of the optical heads, regardless of distance dependency of optical intensity which is a characteristic of the near-field light, a stable signal output is provided and high speed recording/reproduction can be carried out.